MerCathode

Cableguy Greg

I just purchased the Mercury Service Manual for my Bravo 3 drive. I was looking thru and I stumbled across the Mercathode information. I boat in fresh water and I get more than the average amount of corrosion on my drive. I am probably going to replace the electrode because I get the feeling that it has been painted by the PO of the boat. I also stumbled across an interesting statement, "In saltwater, a second MerCathode System blue controller may be added in parallel to increase protection to 400mA." I did the reference electrode test and I recall it being around 650mV in fresh water, which is low, and may be causing some of my corrosion issues. For the test, it gives you acceptable levels for fresh water and "Salt, Polluted, or Mineral Laden water". I have a feeling that the rivers that I boat in, The Allegheny, The Ohio and The Monongahela, are either mildly polluted or full of minerals. I do know that there is minerals in the water. I am wondering if I add a second MerCathode controller, would that give me the added protection that I need or would it be a waste of money.

Handymans342

I think Pittsburgh gets rain with the highest acid count on the country

Trashman

Try the new mercathode first.  Your old one may have had issues.  I did mine, it's tons of fun.   If you had corrosion issues I'd switch out the hydraulic manifold also.  The wire is quite difficult to fish through.  I used some weed whacker line as a fish tape.   I tied a string to the old one then pulled through but the string came off.   

Stodge

@Cableguy Greg are you eating up anodes fast?  Could the issue be stray current in the area around your boat?

Trashman

Good point stodge. And what type?   Also there could be an issue with your grounding wires/ continuity 

Cableguy Greg

They never go below 50% in a season. I have disconnected all of the boats at the end of the dock where my slip is at and the numbers never change. I am going to start with a new electrode and test the controller. I am sure that it will be FUN to pull the new wires thru with the engine in place. I do have a fiberglass fish tape, which make pulling wires on the boat easier.

Cableguy Greg

I use magnesium anodes, which are for fresh water.

rasbury

thank the lord I don't have to worry about this as I trailer my boat. I have no clue how all this stuff works!

frenchship

Raz,
even if you trailer your boat, has nothing to do with the mercathode or anodes, if you leave your boat in the water even for a week or a few days damages could happen specially in salt water.

rasbury

@frenchship
yes, I figure that....I don't see any corrosion on the foot anywhere except right where the lines for the trim go into a manifold of sorts- right there I have a little.  There is one other small area on the foot, I guess it is an exhaust area (?) where the paint had come off and I repainted it...right by the hex nuts that hold the lower and upper foot together. I guess I better start to figure this out, where do I start? I need something that would explain it to a 5th grader.....

Cableguy Greg

I checked the electrode and it doesn't look to be in the greatest of shape. I will have to reference the manual to see how to test it before buying a new one. I am still considering adding another controller to beef up the system. My spring project list is growing...

Handymans342

Greg, got a pic of that electrode?

rasbury

Anyone know a good reading source that explains what the system does and what makes it work? I do not have a clue like I already stated....electrical and me do not speak the same language...

Trashman

This could be helpful
http://www.boatfix.com/merc/servmanl/14/14a7.pdf


https://www.linkedin.com/pulse/common-corrosion-damage-mercruisers-bravo-3-outdrives-travis-palmer

Cableguy Greg

@Trashman, the Linkedin post confirms what I was thinking about adding a second controller. It also states about replacing anodes, which I will have to start doing twice a season. Mine were beyond the 25% threshold, but others recommend 50%.  I read the Service Manual #28 which is specific to my drive and that is where I got the idea about the second controller. I will grab a picture of the electrode sometime this week. It may or may not need replaced, or I should replace it for peace of mine.

Trashman

@Cableguy Greg  glad that helped. I used magnesium anodes with what i think was a successful 5 month season. im in the delaware river and most at my marina use aluminum. I refinished my severly corroded outdrive at the beginning of the season(i have a discussion with many pics you can check out). I just replaced the mercathode and a new continuity kit on mine and im glad I did. 

rasbury

Ouch, that makes my brain hurt..to long a day today to digest that Greg but thanks, will take a look...i only have a meter with the probes, so if I put the alligator clips on then , does that make the testing accurate?

Cableguy Greg

Here are a couple of pics of the drive unit.

Michael T

@Cableguy Greg. The reference anode test is inaccurate 95% of the time (past Mercury info sheet). If there is any current or slight wave action in/on the water the MAs under-report. The Mercathode module is easily damaged by being hit by anything. Mercuiser has acknowledged this. The system works great but is sensitive. You can gang two together but unless you are boating in the love canal you shouldn't have to. You have done your homework by checking for poor electrical grounds in the boats near you. Is your galvanoic isolator working well - knowing you, I assume you have checked that. I have never let my anodes go below 50%. IMO at less that 50% other surfaces start getting attacked.

Hamdog

My anodes lasted 5 years. They were down to about 30% when I changed them. No damage. Magnesium in fresh water lake.

Handymans342

Has anyone replaced their Mercathode Anodes?????

Handymans342

Hey Greg, Nice steel leader drain plug! Complete with slime! LOL

Cableguy Greg

My oil drain hose is on the other end of it. The small cable that connects to the drain plug fell apart so I have to replace it when I get home from Florida.

Cableguy Greg

I replaced my mercathode anode today. It was a PITA. Hopefully it works better than the old one. The orange wire on the old one was shot.

Handymans342

No pics????

Cableguy Greg

As a follow up, I have much less corrosion this year than what I have had in the past. I believe the new mercathode is working. The old one clearly wasn't.

rasbury

Ugh....i know nothing about this...

aero3113

rasbury said:

Ugh....i know nothing about this...

@rasbury , you don’t have to worry as much since you trailer your boat. But either way, the mercathode system is good to have.

rasbury

Is that the bar mounted on the transom with wire going every where ? How does one inspect it?

reneechris14

it's mounted on the bottom of the gimbal housing. Can check voltage up by the gear lube reservoir or by that thin wire in the pic above,very low voltage like 3 volts I think. 

Willhound

@reneechris14 when you test for voltage do you run a wire back to a negative post on the battery for ground?